Enhanced mechanical properties of re-entrant auxetic honeycomb with self-similar inclusion

A new auxetic honeycomb configuration is proposed by adding self-similar inclusion to the conventional re-entrant hexagonal structure. Theoretical models of the elastic mechanical property are developed for both auxetic honeycombs. The new re-entrant honeycomb exhibits enhanced auxeticity and stiffness compared to the original structure. Both experimental and numerical simulation methods are employed to investigate the in-plane compressive behavior of the auxetic structures, and they show good agreement. The dramatic increase in stiffness observed in the stress–strain curve of the novel auxetic structure can be attributed to self-contact during compression, leading to a significant escalation in plateau stress. The specific energy absorption of the new auxetic structure is approximately 10 times greater than that of the original structure. In addition, the new design enhances the stability of compressive deformation, resulting in a more consistent negative Poisson's ratio effect. A parametric study of the inclusion's geometry is also conducted using the validated numerical model, demonstrating that the concave angle of the inclusion is a key parameter to influence the energy absorption capability and compressive stability. Reducing the height-to-length ratio of the entire structure can significantly prevent its buckling. The proposed auxetic honeycomb exhibits significant potential for application in protection engineering, due to its superior stiffness and energy absorption capacity.